1. Technical Field
The present disclosure relates to a semiconductor memory device, and more particularly, to a deskewing method and apparatus and a data reception apparatus using the deskewing method and apparatus in a semiconductor memory device.
2. Discussion of the Related Art
As the speed of communications between semiconductor chips increases, skew and jitter in data transmitted between the semiconductor chips become more severe and problematic. Accordingly, in order to restore desired data during communication between semiconductor chips, clock skew and clock jitter must be minimized for data transmitted between the semiconductor chips.
To improve communications, a method of matching printed circuit board (PCB) lines or signal lines in a semiconductor chip is used. This method, however, imposes restrictions on the routing of signals, thereby increasing manufacturing costs.
Furthermore, even though PCB lines or signal lines are properly matched with one another, data skews are likely to occur due to inevitable factors such as manufacturing process, voltage, and temperature variations. Due to such data skews, errors in the restoration of data are inevitable. Thus, it is necessary to develop improved methods to restore data in consideration of these data skews.
Furthermore, with the ever-growing demand for low power consumption semiconductor devices, semiconductor memory devices supporting a power down mode to reduce power consumption have been manufactured. While semiconductor chips that support the power down mode are powered on and off, however, jitter accumulates. Such accumulated jitter adversely affects the restoration of data.
In order to address the problem of restoration of data due to skew and jitter in data signals, an analog deskewing method has been suggested. The analog deskewing method, however, is likely to result in long lock times. In addition, when the analog deskewing method is applied to the situation when there are few logic level transitions in a data signal, that is, data value variations, leakage is likely to occur, thereby failing to properly maintain a locked state. In order to maintain a locked state, power is continuously required to be consumed. In this regard, it is necessary to perform a deskewing operation in a digital manner.